Vessel for conveying and storing liquefied gases



Patented June 9, 1925.

UNITED STATES WILHELM norm, oE-HANAU-oN-THE-MAIN, GERMANY.

VESSEL non ooNvEYrNc AND sronme LIQUEEIED GASES.

Application filed'l il'anu'aryl 3, 1921. Serial No. 434,822.

(GRANTED UNDER THE PROVISINS 0F THE ACT 0F MARCH 3, 1921, 41 STAT. L., 1313.)

To all 'whom t may conc-em.'

Be it known that I, WILHELM RGHN, a citizen of the German Republic, residing at Hanau-on-the-Main,` Germany, have in'- vented certain new and useful Improvements in Vessels for Conveying andl Storing Liqueied .Gases (for which I have filed an application in Great Britain, July 12,r

1920, No. 20,988, and have been granted a patent in Germany lSept. 9', 1919, No.

302,532), of which the following is a speci-A Ai'fation.v l

Dewars glass vessel with walls lined with a 4reflecting agent represents an almost ideal contrivance for conveying 'and Storing small quantities of liquefied gases. For larger quantities vessels of metal have been made on the same principle and their insulating properties were also fairly satisfactory. But an arbitrary enlargement of such vessels is not possible because exceedingly large vessels cannot be made suficiently gas-tight to maintain a satisfactory vacuum, and besides the weight is excessive. For this reason vessels for the storage of liquid air have been proposed by American inventors (see U. S. Patent- 673,- 073) that are constructed on diderentlines. These vessels 4are not subject to limitations of size and yet possess satisfactory insulating properties without being excessively heavy. The vessels built according to this)y plan consist of a number of insulating shells, one within the other, that are filled with wool-waste, feathers, felt or the like, and in o r between which -the cold evaporated gases engendered by the liquid air are caused'to stream. But these vessels still fall far short of the most favorable resultsu that may be obtained by further consistently applying this principle. They fail utterly' where liquid hydrogen (for ininstance) is to be stored and conveyed because the insulating capacity of such agents as wool, feathers, felt or the like that are lled with hydro enl is five to eight times worse than that o the same materials filled with air. Since in addition to this the amount of warmth required to evaporate one litre of liquid hydro en islive timesas small, and the'A chilling e ect of the cold gas produced from a litre of liquid hydrogen is only one and a half times greater than that of liquid air, the time for which a vessel for liquid hydrogen constructed according to the said American plan would satisfactorily store liquid hydrogen would be ten times shorter than that for liquid air. (Dewar vessels are also three to three anda half times worse for liquid hydrogen particularly desirable as this would be a convenient means for supplying such consumers as autogenous welding works and airships whose dimensions areV being continually increased. The hydrogen, instead of being conveyed in steel bottles in the form of a compressed gas, would then be transported in the afore-described vessels in a liquid state, and an enormous `saving in the Weight to be carried would then be achieved.

A vessel that is suitable for liquid hydro-l gen would also be'4 eminently adapted for any other gas used for ,technical purposes, because it is just in the case of liquid hydrogen, whose heat of evaporation is small and which is an extraordinarily good con-y ductor of heat,l that the problem is particularly diflicult kto solve.

A type of vessel is hereinafter described that is equally eliicient for all liquefied gases including hydrogen and which'possesses much higher qualities than any of the previously proposed lvessels and may be made much lighter than the.

A. diagrammatic cross sectional view'of .suitable insulating agent such as feathers, lcork dust, magnesia etc. Circulation spaces Aare left between each pair of insulating shells so that three o Aformed that are bounded by the sheet metal walls b and o, d and e, f and g.. The cold gas that evaporates in the innermost vesthese spaces 'are 4 said walls a small pipe o, p, g, r, lthrough which a suitable gas may be injected into the shell, leads to the exterior.

The gases chosen for filling the shells will be decided bythe following facts: Experiments will show that the insulating properties of a certain packing material, say

lfeathers, will improve the nearer the aver-` age temperature of the particular insulating space is to the temperature of condensation of the particular gas used for filling the said space, so that for example the insulating properties ,of a certain space filled with feathers and air is four to five times as good at about 160 Celsius as it is-at 0 Celsius. Hence the insulating properties of such vessels having various insulating shells which are stuffed, say, with feathers, can be cousiderably increased by charging the shells with gases whose points of condensation are just a little lower than the average temperature existing in their interior. done the points of condensation of the gases in the series of shells, commencing from the interior, will rise from shell to shell. Thus if the vessel is to contain hydrogen the innermost shell ,would be charged with hydrogen, the next with nitrogen, the next withv nitric oxide, and the next with carbonic acid in order to obtain the most favorable insulating properties. c

It can also be demonstrated -by experiment that the insulating capacity of a layer of feathers (for instance) of a certain thickness'at so low a temperature is not by any means increased more and more by stuliing more and more feathers into the space in question, as is the case at an ordinary tem- -perature. In reality, at low temperatures there is a definite density of the feathers for 5 each kind of gas at which Athe highest pos- 5 sible insulating capacity is reached, whilst a further increase of the density of the feathers only causes an increase of `weight without improving the, insulating qualities. Hence, to obtain the smallest possible weight, the feathers stuffed into each shell a will preferably be only of such a quantity that the density most favorable for insulating purposes is attained. (This degree of density is obtained for instance with a certain kind of downy feathers, at\a tempera- If this is`- ture. of V Celsius and with an Yain charge, when 20 grams of feathers are used per litre; or under the same conditions but with a hydrogen charge when 50 to 70 grams of feathers per litre are employed.) 1

In the similar kinds of vessels heretofore'f'e employed the various insulating shells were made equally thick at all of their parts. But by a simple consideration the factfis revealed that the thickness .of the insulating layer or shell should be proportional at each point to the difference of temperatures eXiste ing thereat between the inner and outer surfaces of the shell. temperatures between the inner and outer sides of an insulating shell is always approximately zero in the neighbourhood of the openings la, Z, m, n that connect one circulating space with the next and the, 'greatest difference is reached at the point opposite to, or furthest away from, the particular opening. Hence the insulating shells are preferably made of taperingcross-section as indicated in the drawing, by which measure the insulating capacity is increased in a ratio of 1:1,6 with the same amount of insulating material, or, with an equal insulating capacity, a saving of 30% by weight is accomplished.

In this manner vessels can be produced that are capable of storing 1000 litres of liquid air for more than 60 days, or liquid hydrogen for about 30 days, so that they are even better for liquid air than the vessels constructed on Dewars priniple. In addition, their weight only amounts to 0.2 to 0.5 kg. per cubic metre of gas `obtainable from them, whilst the steel bottles now employed for conveying gases underpressure weigh about 12 to 15 kgs. per cubic metre of as.

Iiginally the described type of vessel according to the invention enables the s eed of evaporation to be easily regulate by putting one or more circulating spaces out of action. Formerly attempts were made to accomplish this by dipping metal rods to various depths into the liquid gas to be evaporated; but the protruding ends of the rods soon became coated With ice which lrendered their effect insufficient. To obtain satisfactory results with the vesselconstructed according to the inventlon the gas,

instead of being allowed to pass out through 1. A. vessel for storing (or conveying)` liquefied gas consisting of a plurality of hollowl shells .placed one within the other,

Thus the difference cof,

- the highest possible insulating eiect,sul1

' the shell at the various oints.

the hollow space in each shell being filled with insulatin material and gas, the gas being of a whose point of condensatlon is as little'below the average temperature existing in the said space as is possible under practical conditions, and the quantity of the said insulating materialbeing such that the particular combination of the density of the material and temperature is obtained that produces as nearlyv as possible stantially as described.

2. A vessel for storing (or conveying) liquefied gas consisting of a plurality of hollow shells placed one Within the other, the hollow space in each shell bein iilled with insulating material and gas, t e gas being of a kind whose point of condensation is as little below the average temperature existing .in the said space as is possible under practical conditlons, the vquantity of the said insulating material being such that the particular combination of the density of the material and temperature is obtained that produces as nearly as possible the highest possible insulating eiect, and the thickness of the said shells differing at their varicls parts in proportion to the differences of temperature existing thereat between the inner and the outer surfacedof 8./ A vessel for storlngv (or conveying) liqueed gas consisting of a plurality of hollow shells placed 4one withini the other so as to leave 4a circulation space between'each two shells, the hollow space in each shell being lled with insulating material and that the particular combination oflow spaces to the circulation spaces, and a pipe or pipes) associated with the said cir'- culation spaces so as to aord communication between the latter and the exterior of the vessel and adapted to increase or decrease the number of circulation spaces traversed by the saidv gas, whereby the speed of evaporation of a gas contained in the vessel may be regulated within wide limits.

4. A vessel for liquefied gas comprising a reservoir for the liquid gas with a double-wall envelope, insulating material between the walls of the envelope, and a gas between the walls of the envelope which is of such a kind that, at-the temperature to which it is subjected,'it is just above its point of condensation.

In testimony whereof `-I have signed this specification in the presence of two witnesses.

DR. WILHELM ROHN. Witnesses:

WILHELM Hmmm, Frl'rz GnMoLL. 

